The DirectX 10 (DX 10)-based graphics cards are here, and those who believe the transition from DirectX 9 might be just a footnote in gaming history are sadly mistaken. DirectX 10 is the next generation in how games are created; it's what industry experts are calling, "a giant leap forward." The DX 9 games were officially tapped out; their limits stretched to the end on what you could maximize out of the card. When talking about the transition from DX 8 to DX 9, gaming enthusiasts might not even recall the transition because the changes were minimal compared to the advancements we will see in the latest upgrade.

Link: http://www.gamepyre.com/hardwared.html?aid=854&p=1